Field of Invention
The present invention relates to the technical field of satellite gravity field measurement, and more particularly to a method for parsing and calculating performance of satellite gravity field measurement by low-to-low satellite-to-satellite tracking, which is applied for parameter design of a gravity field measurement satellite system by low-to-low satellite-to-satellite tracking.
Description of Related Arts
As a basic physical field of the earth, gravitation field is an important application in earth science research, land resource exploration and geological disaster forecast, and thus the gravitation field has always been an essential issue in geodesy. With the developments of space technology, satellite gravity field measurement attracts more and more attention due to the unique advantages of high coverage, all weather, and without affection by geopolitics and geographical environments. The satellite gravity field measurement has obtained substantial progress in theoretical research and engineering practice and become the most effective way to obtain the global gravity field model[1,2].
Depending on differences in data observed, the gravity field measurement is classified by three principles of orbit perturbation, low-to-low satellite-to-satellite tracking and gravity gradient[3], wherein the orbit perturbation principle is suitable for low-order gravity field measurement which has main observation data of a gravity gradient orbit; the low-to-low satellite-to-satellite tracking principle is suitable for a medial-to-high order gravity field measurement which has main observation data of a distance between two low earth orbit satellites and a change rate thereof; and the gravity gradient principle is suitable for a high-order gravity field measurement which has main observation data of gravity gradient value. The gravity satellites which are successfully implemented or under developed all adopts the measurement principles mentioned above or a combination thereof. E.g., CHAMP utilizes the orbit perturbation principle to recover low-order gravity field; GRACE Follow-on and NGGM satellites utilize both orbit perturbation principle and low-to-low satellite-to-satellite tracking principle to recover medial-to-high order gravity field; and GOCE respectively utilizes orbit perturbation principle and low-to-low satellite-to-satellite tracking principle to recover the low gravity field and the high gravity field. Though, the three principles are respectively suitable for different frequency band of gravity field measurement, the effective order and accuracy of the gravity field measurement are mainly depends on load indicators of the gravity satellite. Under the medial or high order gravity field measurement by low-to-low satellite tracking and gravity gradient orbit, analyzing from the current load performance indicator, the low-to-low tracking measurement is absolutely capable of reaching or even exceeding measurement level of gravity gradient. Therefore, the symposium named “Measurement of satellite gravity field in the future” held in 2007 in Holland decided that the subsequent international gravity satellite continues adopting the low-to-low satellite-to-satellite tracking manner, and that parameters of the system are considered to be improved to increase the measurement performance of the gravity field.
In the conventional design of orbit parameters and loading parameters of gravity field measurement system by low-to-low satellite-to-satellite tracking, a numerical simulation method is mainly utilized to analyze the impact of system parameters on measurement performance of gravity field, so as to further determine design parameters of the system. However, the simulation of gravity field measurement is in high demand of performance of computers, and calculation time lasts very long, which is not conductive to analysis of influence rule of the system parameters on the gravity field measurement, and not convenient for the optimal design of system parameters. In order to overcome the shortcoming, based on the principle of conservation of energy, the present invention establishes an analytical method for gravity field measurement performance by low-to-low satellite-to-satellite tracking, so as to obtain gravity field measurement performances such as an effective order of the gravity field measurement, a geoid error and gravity anomaly error, and determine the influence rule of the system parameters on the gravity field measurement. Thus, the present invention has great guiding significance on parameter design of gravity satellite system by low-to-low satellite-to-satellite tracking.